I'm giving this post a "bump" in the hopes that one of the resident gurus chimes in... I've never heard that "some neutral density filters are sensor dependent" or that "IR bleeds into the image" and I use a 5D3 not a T4i. But I'm always willing to learn something new... And if true, it just may explain why I sometimes (usually with very long exposures) find the "sickly warm" color-cast of the B+W 10-stop ND filters nearly impossible to correct!

I believe that all ND filters have some version of a color-cast to them. The highly regarded Lee Big Stopper for instance has a very pronounced blue-cast. I find most all of these color-casts are generally very easy to correct with AWB or in post. That is with the exception of my B+W 10-stop filters! Not always, but there are times when the B+W's color-cast is uniquely difficult (if not impossible) for me to easily correct.

Now obviously I'm not at all certain what is going on in these situations, but it's almost as if there are two different color-casts happening in the same image (at the same time) -- a warm (pink-ish brown) in the highlights, mid-tones & quarter-tones, and a cool (magenta-ish blue) in the shadows & 3/4-tones... I know that it is quite a long-shot, but maybe your "IR bleeds" are the reason behind the issues I occasionally have with the color-cast of B+W 10-stop ND filters...

Tiffin is not particularly noted for high quality filters, probably because they sell a lot of low end ones. Their high end ones are said to be good. They have announced a new 10 stop ND filter at CES that they claim will not tint images. Expect to pay more for it, the price is not available yet.

Thanks for the input.Thanks for the Bump, Oregon. (I lived in Portland at one point). From what I have learned from the web, some sensors have an IR filter on them and will not have as much of a problem with the IR bleedthrough.

I don’t mind dealing with a little color cast. In the pic I posted, the red on the ends of the boughs is impossible to get out. And, yes the cast is dependent on the deepness of the tone.

I am using the new Tiffen ND 3.0. All the reviews say little color cast. I called Tiffen a few days ago. They must have heard from others because they said they were aware of the problem and would get back to me. In the mean time I will return the filter. I was thinking about a different ten stop, maybe the B+W, but I am not sure if it will react the same way to my sensor. Aaaargh.

From what I have learned from the web, some sensors have an IR filter on them and will not have as much of a problem with the IR bleedthrough.

All dSLR sensors have an IR cut filter on them. None of those filters are perfectly effective at blocking all IR light with long daytime exposures, so you'll get some bleed through.

There's a type of filter called a 'hot mirror ND' or IRND filter, which is basically a neutral density filter plus an IR cut filter. The combination of a filter like that and the IR filter on the sensor is effective at eliminating the IR bleed. However, I haven't seen them in a 10-stop version (6 is the most I've seen) and they don't work with wide angle lenses.

Thanks Neuro. Looks like the ND filters are in some ways still in their infancy. I am curious if my results are truly sensor dependent. Maybe each camera's sensor cuts off IR at slightly different wavelengths. The frontier of filters...

Anyway.

I got a hold of a Hoya ND400 filter, though it is not mine. Here are the results. It looks like the Hoya does a good job of blocking out the IR/nearIR. It has a slight cast, which is expected. Compared to the Tiffen, it is a slice of heaven.

I like the B+W nd110, but may get the Hoya just because I know there is very little cast (on my sensor?!?!?!)

Here is a quick & dirty test of my "heavy" ND filters, courtesy of my neighbor's front yard... Now these exposures are only in the 1-second range so they're not long enough to test for "IR bleed-through," but simply demonstrate the different colors associated with these heavy ND filters. As you can see, the Haida filter appears to be the most color-neutral in this situation, and the B+W appears to be a reasonably close second-place. While the (second place) B+W filter doesn't appear to have a heavy color cast, it can be real hell to correct in a long exposure. The Haida is a new purchase for me so I don't yet have any experience color-correcting it when used in very long exposures. Ironically, the widely popular Lee Big Stopper easily has the heaviest (blue) color cast, but I find it to be a piece of cake to correct in post! Go figure... Maybe the blue color cast filters out some of the "IR bleed-through," I don't know... BTW, by "long exposures" I'm talking 2, 4, & 8 minutes.